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author | Vincent Donnefort <vincent.donnefort@arm.com> | 2021-06-21 11:37:52 +0100 |
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committer | Peter Zijlstra <peterz@infradead.org> | 2021-06-22 16:41:59 +0200 |
commit | d7d607096ae6d378b4e92d49946d22739c047d4c (patch) | |
tree | 0df59f0fce007681a493960a9caeee22023a9589 /kernel | |
parent | fecfcbc288e9f4923f40fd23ca78a6acdc7fdf6c (diff) | |
download | linux-d7d607096ae6d378b4e92d49946d22739c047d4c.tar.bz2 |
sched/rt: Fix Deadline utilization tracking during policy change
DL keeps track of the utilization on a per-rq basis with the structure
avg_dl. This utilization is updated during task_tick_dl(),
put_prev_task_dl() and set_next_task_dl(). However, when the current
running task changes its policy, set_next_task_dl() which would usually
take care of updating the utilization when the rq starts running DL
tasks, will not see a such change, leaving the avg_dl structure outdated.
When that very same task will be dequeued later, put_prev_task_dl() will
then update the utilization, based on a wrong last_update_time, leading to
a huge spike in the DL utilization signal.
The signal would eventually recover from this issue after few ms. Even
if no DL tasks are run, avg_dl is also updated in
__update_blocked_others(). But as the CPU capacity depends partly on the
avg_dl, this issue has nonetheless a significant impact on the scheduler.
Fix this issue by ensuring a load update when a running task changes
its policy to DL.
Fixes: 3727e0e ("sched/dl: Add dl_rq utilization tracking")
Signed-off-by: Vincent Donnefort <vincent.donnefort@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lore.kernel.org/r/1624271872-211872-3-git-send-email-vincent.donnefort@arm.com
Diffstat (limited to 'kernel')
-rw-r--r-- | kernel/sched/deadline.c | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index 22878cd5bd70..aaacd6cfd42f 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -2497,6 +2497,8 @@ static void switched_to_dl(struct rq *rq, struct task_struct *p) check_preempt_curr_dl(rq, p, 0); else resched_curr(rq); + } else { + update_dl_rq_load_avg(rq_clock_pelt(rq), rq, 0); } } |